Conventionally, artificial sueded leathers have been widely developed as a luxury apparel material. These artificial sueded leathers comprise a nonwoven fabric, woven fabric, or knitted web made of ultra-fine thermoplastic synthetic fibers into which an elastomer such as polyurethane is impregnated, and whose surface is formed by buffing to raise the thermoplastic synthetic fibers thereof.
In recent years, these artificial raised-fiber sueded leathers have been developed not only for applications in apparel, but also for applications as industrial materials, such as for automotive upholstery (e.g., for the seats and interiors of luxury cars), wheelchair upholstery, furniture/interior applications such as wall materials, and for construction.
In these non-apparel fields of application, there have been demands in particular for a material having extremely high flame retardant properties.
For this reason, a variety of investigations were conducted with an aim to overcome the below problems (a) through (d) that are particular to artificial sueded leathers and not to typical woven/knitted materials made of synthetic fibers, in order to realize flame retardant properties exceeding the flame retardance at the level of the conventional art.
(a) There are gaps in the inter-fiber portions of the standing fibers, and structurally, the material is easily flammable.
(b) The flame retardant mechanisms for the elastomer and the thermoplastic synthetic fibers are different.
(c) The flame retardant reduces the appearance, the surface quality, and the light resistance of the artificial sueded leather.
(d) The flame retardance process leads to a lowering of the color fastness of the dye and texture hardening.
A method for solving the above-described problems (a) through (d) has been proposed wherein a halogenated phosphate ester is applied along with an acrylic acid ester resin to the reverse face of the raised-fiber surface (Patent Literature 1).
In addition, a method has been proposed wherein flame retardant is included in advance in the elastomer of polyurethane or other material that is impregnated in a nonwoven or other fabric (Patent Literature 2).
In addition, a method has been proposed that uses thermoplastic synthetic fibers whose organic phosphorus components have been copolymerized (Patent Literature 3).
However, although the method of Patent Literature 1, wherein a halogenated phosphate ester is applied along with an acrylic acid ester resin to the reverse face of the raised-fiber surface, is excellent in flame retardance, there are problems in that, due to the halogen, poisonous halogen gas, dioxins, and halogen compounds generated during burning accumulate inside living organisms.
In addition, in the method of Patent Literature 2, wherein flame retardant is included in advance in the polyurethane that is impregnated in a nonwoven fabric, there are problems in that the degree of polymerization of the polyurethane decreases over time. Since the polyurethane or other elastomer can become brittle, long use can lead to deterioration in the strength of the artificial raised-fiber sueded leather, which can then lead to not only tearing, wear from friction, fluffs and residual strain, but also lower the color fastness to light of the dye.
In addition, in the method of Patent Literature 3, wherein thermoplastic synthetic fibers whose organic phosphorus components have been copolymerized are used, there is not only the problem of the increased production costs that accompany the investment into polymerization equipment and switching product stock, but also the inevitable problems of the insufficient strength characteristics particular to copolymerized fibers, and the insufficient color fastness to light.
In addition, a sueded fiber structure has been proposed wherein a resin composition, which includes an acrylic acid ester resin as the primary component as well as an aromatic phosphate ester compound and a metallic oxide, is applied to the surface of the thermoplastic synthetic fiber fabric that has a raised-fiber portion at the surface thereof. This sueded fiber structure has been proposed as having excellent fire prevention properties including self-extinguishing properties, and additionally, has excellent texture and no lowering of color fastness; moreover, poisonous gases such as dioxins are not readily generated during incineration (Patent Literature 4).
In addition, a sueded fiber structure having a raised-fiber portion on the outer surface thereof has been proposed wherein an acrylic acid ester resin and an organic fluorinated polymer-type water repellant are imparted to the sueded fiber structure. Additionally, an acrylic acid ester resin composition, which includes an aromatic phosphate ester compound and a metallic oxide, is imparted to the inner surface of the sueded fiber structure. This sueded fiber structure has been proposed as having excellent fire prevention properties and melt resistance; in other words, the fiber structure has excellent fire prevention properties and melt resistance including self-extinguishing properties, and additionally, has excellent texture and no lowering of color fastness. Moreover, poisonous gases such as dioxins are not readily generated during incineration (Patent Literature 5).
In addition, an artificial leather has been proposed wherein a flame retardant composition is imparted to one face of a fabric, the flame retardant composition including a binder resin, at least one phosphate compound selected from the group consisting of guanidine phosphate, ammonium polyphosphate, melamine polyphosphate, and phosphoramides, as well as at least one compound selected from the group consisting of pentaerythritol, dipentaerythritol, melamine, dicyandiamide, starches, celluloses, and sorbitol, and the fabric being a woven fabric, a knitted web, or a nonwoven fabric including synthetic fibers having a single-fiber fineness of not more than 1 decitex and including an elastomer. This flame-retardant raised-fiber artificial leather has been proposed as having excellent flame retardance, light resistance, and wear resistance, as well as being non-halogenated (Patent Literature 6).
However, in the related art regarding flame retardance in Patent Literature 4 and 5, automobile seats melted while burning during a FMVSS No. 302 test of horizontal burning speed, a flammability testing method. For this reason, adapting the related art to pass this test has been difficult.
In addition, although that which is described in Patent Literature 6 has acceptable flame retardance, this related art still has problems regarding water spot.
Patent Literature 1: Japanese Unexamined Patent Application Publication No. S58-013786
Patent Literature 2: Japanese Unexamined Patent Application Publication No. H7-18584
Patent Literature 3: Japanese Unexamined Patent Application Publication No. 2002-294571
Patent Literature 4: Japanese Unexamined Patent Application Publication No. 2004-36011
Patent Literature 5: Japanese Unexamined Patent Application Publication No. 2004-308051
Patent Literature 6: Japanese Unexamined Patent Application Publication No. 2005-2512